Xerographic imaging employing a selectively removable layer



Filed Dec. 2, 1964 May 27, 1969 CLARK 3,446,616

XEROGRAPHIC IMAGING EMPLOYING A SELECTIVELY REMOVABLE LAYER 7} Sheet of 2 FIG. I

FIG. 4 FIG. 5

INVENTOR HAROLD E. CLARK BY QM 6 ATTORNEYS y 27, 1969 H. E. CLARK 3,446,616

XEROGRAPHIC IMAGING EMPLOYING A SELECTIVELY REMOVABLE LAYER Sheet 2 of 2 Filed Dec. 2. 1964 l/V VE N TOR BYWA/g Wa United States Patent 3,446,616 XEROGRAPHIC IMAGING EMPLOYING A SELECTIVELY REMOVABLE LAYER Harold E. Clark, Penfield, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporationof New York Filed Dec. 2, 1964, Ser. No. 415,384 Int. Cl. G03g 7/00 U.S. CI. 96-15 13 Claims ABSTRACT OF THE DISCLOSURE The subject matter of this patent application is directed to a imaging process whereby a particulate image is xerographically formed on a specially prepared imaging member having a selectively separable photoconductive layer. After the particulate image is formed on the special member and without permeately aflixing it thereto, a tacky transfer member is pressed against the image bearing member so that intimate contact will be made with the photoconductive layer in all areas except where prevented by the particulate image. The transfer member and imaging member are then separated thereby forming complementary images on the respective surfaces.

This invention relates to xerography and more particularly an imaging process including selectively adhesively stripping the photoconductive layer from a Xerographic plate. 1

"As described in U.S. Patent No. 2,297,691, and many subsequent patents, xerography may be used to make visible reproductions from an optical image on a photoconductive member with electroscopic marking material. In addition to the widespread commercial application of xerography to reprography, it is also known that xerographically formed powder images may be put to many other uses. For example, xerographically formed powder images-may be used as an effective resist in selective etching process such as those used in producing printed electrical circuits.

It is also known that xerographically formed powder images may be used as a resist in certain imaging processes to permit selective adhesive transfer of marking material from one surface to another. One such method, capable of extremely high resolution imaging, is fully described in copending U.S. application Ser. No. 212,083 filed on July 24, 1962, now U.S. Patent No.-3,275,436. Briefly, according to that disclosure, a uniformly coated donor member is brought into close contact with an adhesive member bearing a Xerographic toner image.

Upon separation of the two members, marking material is transferred to the adhesive member except where prevented by the toner image. Notwithstanding the improvement in high resolution imaging advanced by the aforesaid invention, it nevertheless necessitates the use of a donor member substantially uniformly coated with releasable marking material. Since the preparation and handling of such donor'member is frequently inconvenient, an ir'nproved'system that dispenses therewith is highly desirable. The present invention achieves this desirable result, and has as one of its objects an improved process-'for forming replicas of a master by selectively transferring material from one surface to another by means of adhesive forces. A practical method for labeling packages, vessels, and the like, is also an object of the present invention.

Briefly summarized, my invention includes first xerographically forming a particulate image on a special imaging member having a selectively separable photoconthe special member, and without permanently affixing it thereto, a tacky transfer member is pressed against the image bearing member so that intimate contact will be made with the photoconductive layer except where prevented by the particulate image. The transfer member and special imaging member are then separated whereby portions of the photoconductive layer and the particulate image are removed and transferred to the transfer member. Those portions of the photoconductive layer beneath the particulate image, and hence not contacted by the transfer member, remain on the special imaging member. In a preferred embodiment of the present invention, the selective removal of 'the photoconductive layer unmasks a contrasting background layer. v

The aforementioned objects as well as others that will be apparent to those skilled in the art are achieved by my invention which is hereinafter described in detail in connection with the accompanying drawing. In the drawing:

FIG. 1 schematically illustrates the multi-layer structure comprising the special imaging member used in the present invention;

FIG. 2 schematically illustrates the application of a uniform electrostatic charge to the special imaging member;

FIG. 3 schematically illustrates the formation of a latent electrostatic image by exposure of the sensitized plate to an optical image;

FIG. 4 schematically illustrates a typical xerographic development step;

FIG. 5 schematically illustrates the special imaging member with an image of electroscopic particles thereon;

FIG. 6 schematically represents the novel adhesive stripping process of the present invention;

FIGS. 7 and 8 schematically illustrate the complementary replicas produced in accordance with the present invention;

FIG. 9 schematically illustrates affixing one of the replicas to a support member; and

FIG. 10 schematically illustrates image preservation of a replica produced in accordance with the present invention.

FIG. 1 schematically represents the special imaging member used in the present invention. As illustrated, plate 10 is a multilayer structure comprising a photoconductive layer 11, a release layer 12, a background layer 13 and a conductive backing 14.

In the present invention, this structure is used as a conventional xerographic plate to form a powder image from a master after which certain portions of photoconductive layer 11 are selectively removed. Therefore, unlike conventional xerographic plates, the photoconductive layer of plate 10 is desirably easily fracturable to permit selective stripping from plate 10 by means of an adhesive member.

Release layer 12 is incorporated into the structure to facilitate separation of the photoconductive material. The

preferred embodiment as illustrated also incorporates a sequently, background layer 13 may be omitted where particular applications render it unnecessary. A more detailed description of plate 10 and its constituent layers will be given after the following description of the instant process.

FIG. 2 illustrates sensitization of special image member 10. In the illustrated embodiment, corona generator 21 energized by high voltage power supply 22 is positioned in charging relation with, and moved relative to plate 10 to apply a substantially uniform electrostatic charge. As is usual in xerography, plate sensitization is carried out in darkness so that the electrostatic charge will be retained on photoconductive layer 11.

FIG. 3 illustrates exposure of the sensitized plate to a pattern of light and shadow. Lens 25 is shown focusing an optical image of master 24 (which comprises, for example, a document or three-dimensional subject to be reproduced) on photoconductive layer 11. Since the photoconductive layer is rendered relatively more conductive in illuminated areas, plate 10 becomes selectively discharged and a latent electrostatic image is formed in accordance with the optical image.

FIG. 4 illustrates one method for developing a latent electrostatic image. After it is sensitized and exposed to the optical image, plate 10 is immersed in tank 26 containing developer 27 of electroscopic particles 28 suspended in a relatively nonconducting liquid carrier 29. Depending upon the predetermined electrical properties of the developer components and the polarity of the charge applied to plate 10, the toner particles will be attracted by, and adhere to, either the charged or uncharged areas of plate 10. Although the preferred method for developing a toner image usable in the present invention is illustrated, other developing methods known to the art of xerography may be used if desired, such as those fully described in US. Patents No. 2,297,691; 2,618,551 and 2,638,416.

FIG. represents developed image 31 on plate 10. A fixing step common to certain applications of xerography is not included at this stage of the present process. Rather, the electroscopic particles (commonly referred to as toner particles) comprising image 31 desirably adhere only lightly to photoconductive layer 11 so that they may be easily adhesively removed along with certain portions of the photoconductive layer.

FIG. 6 illustrates the novel stripping process of the present invention. An adhesive transfer member is brought into contact with the image-bearing surface of the special imaging member and then separated therefrom to selectively remove from plate certain portions of photoconductive layer 11 and image 31.

As schematically represented in FIG. 6, roller 35 presses transfer member 32 having an adhesive surface 33 against plate 10 to effect close contact of adhesive surface 33 with photoconductive layer 11 except where contact is prevented by the toner particles comprising image 31. Separation of member 32 from plate 10, accomplished manually or by equivalent mechanical means, results in the transfer of the particulate image and the stripping of toner-free portions of the photoconductive layer which are held in contact with member 32 by adhesive forces. These are indicated in FIG. 6 at 31 and 11', respectively.

FIGS. 7 and 8 illustrate the results of the above process: complementary replicas of master 24. The transfer replica on member 32 is seen in FIG. 7 as particulate image 31' against a background of those portions of photoconductive layer 11 stripped from plate 10. This replica, of course, will appear as the reverse or mirror image of the image xerographically formed on plate 10. If member 32 is transparent, the image can be conveniently viewed in right-reading form, and, if desired, the replica can also be conveniently fastened to another surface with the toner side down, thus producing a protected visible image. A typical application of the latter would be the labeling of a package or vessel. For example, as illustrated in FIG. 9, the replica may be aflixed to support member 38 by pressing member 32 against adhesive material at 39 by means of roller 41.

In FIG. 8 the replica of master 24 is seen as the remaining portions of photoconductive layer 11 against a background provided by background layer 13. If image preservation is desired, this replica may also be conveniently protected in any conventional manner such as plastic lamination coating with lacquer, or the like. For example, as illustrated in FIG. 10, a protective coating may be applied by spraying lacquer 42 or other suitable protective material over member 10 by means of pressure chamber 43.

The following example is illustrative of the present invention, but limitation to the specific materials and xerographic processing steps should not be inferred. A wide variety of equivalents may be employed without departing from the invention as defined by the appended claims.

Example The black side of conductive wet strength paper (Crocker and Hamilton Papers, Inc.; E. P. Graphics Cls. Grade T-62-5-16A, is coated by means of a No. 10 wire wound bar, with a solution comprising, by weight: 5 parts of Syl-off 23 silicone-type release coating, 1 part of Syl-off catalyst 23A (Dow Corning Corporation), and 99 parts of xylene solvent. The coating is cured at 250 F. for five minutes to form a continuous, solid, non-blocking film.

A dispersion is prepared by milling in a stainless steel paint shaker: 1 part of orange shellac (47% solids in alcohol; Parks Company), 2 parts ethyl alcohol and 2 parts zinc oxide U.S.P. (Fisher Scientific Company). The dispersion is then coated over the cured release layer by means of a No. 20 wire wound bar, and air dried to form the photoconductive layer. This comprises the special imaging member (plate 10 in the drawing) which is used to form a toner image by means of conventional xerographic process steps.

Specifically, a negative uniform electrostatic charge of about 200 volts is applied to the coated surface in darkness by means of a corona discharge electrode. The sensitized member is then selectively discharged by exposure to an optical image of a transparency from a photographic enlarger. The latent image thereby formed is developed by immersing the member in a development tank containing liquid developer of 1 part, by weight, of Velva-Glo chartreuse pigment type P-1500G3l0 (Radiant Color Corp.) dispersed in 99 parts Freon 113 trichloro trifiuoro ethane (E. I. duPont de Nemours and Company). The pigment particles deposit at the charged areas of the imaging memher to produce a positive image of the transparency. No. 853 Mylar adhesive tape (Minnesota Mining and Mannfacturing Company) is applied to the image-bearing member by means of a rubber roller under hand pressure. Manual separation of the tape and image member results in (l) stripping of the pigment particles and the particlefree areas of the photoconductive layer from the image member, and, (2) the unmasking of the black surface of the paper base of the imaging member except where unstripped portions of the photoconductive layer remain. Thus, two replicas are produced: on the tape, pigment particles in image configuration against an opaque gray background of stripped portions of the photoconductive layer; on the image member, remaining portions of the opaque gray photoconductive layer in image configuration against a black background.

Since only those portions of photoconductive layer 11 actually in contact with adhesive surface 33 of member 32 are to be removed from plate 10, photoconductive layer 11 must be so constituted as to adhere to member 32 and to selectively fracture as the elements are separated. Binder layer formulations commonly used in xerography are generally too plyable for use in the present invention as they would tend to be completely, rather than selectively, removable under the adhesive forces exerted upon separation of the members. Specially prepared members are therefore preferred.

Conventional xerographic binder plates commonly include a photoconductive layer of photoconductive material dispersed in a resin binder coated on a relatively conductive support backing. These usual constituents may be used in the present invention provided that the ratio by weight of photoconductive pigment to binder is at least about 2 to 1. Much higher ratios are also usable, and ratios of as high as 20 to 1 have been found to produce photoconductive layers that are easily fracturable by the adhesive forces, yet not so delicate as to be unsuitable for use in the present invention.

Any particulate photoconductor known to the art may be used. These include, but are not limited to, zinc oxide, cadmium sulfide, zinc sulfide, zinc-cadmium sulfide, zincmagnesium oxide, cadmium selenide, zinc silicate, calcium-strontium sulfide, mercuric iodide, titanium dioxide, and zinc titan-ate as well as many known organic photoconductive materials.

The following are typical of the many suitable binder materials known to the art: polystyrene; silicones resins such as DC801, DC-804 and DC996 (Dow Corning Corp.) and FR-SZ (General Electric Co.); acrylic and methacrylic esters polymers such as Acraloid A and Acraloid B 72, polymerized ester derivatives of acrylic and alpha-acrylic acids (Rohm and Haas Co.) and Lucite 44, Lucite 45, and Lucite 46 polymerized butylme-thacryl ates (DuPont de Nemours and Company); vinyl polymers and copolymers; and mixtures thereof.

Conductive backing 14 may comprise a metal plate, a metalized plastic sheet or a carbon-impregnated paper, or any other suitable relatively conductive backing known to the art.

The electroscopic particles used for producing image 31 may be pigmented or non-pigmented depending upon the particular application of the present invention. The particles need function only as a resist between the adhesive member and the photoconductive layer, and therefore, the respective colors or densities of the various elements need be considered only insofar as needed to provide suflicient contrast for readability.

Two-component Xerographic developers, commonly used to :produce toner images on xerographic plates are conveniently usable in practicing the present invention. If a liquid development method is used, as described in connection with the preferred embodiment herein, the developer may comprise electroscopic resinous particles suspended in a non-conductive liquid carrier. However, since the present invention is not limited to any particular process of xerography, any of the wide variety of commercially available xerographic developers may be used with the appropriate xerographic developing process. Suitable developers are also described in the patent literature, such as in US. Patent No. 2,618,551 to Walkup.

In addition to the release coating already mentioned, layer 12 may comprise other suitable materials such as for example, paraffin wax, miner-a1 oil, soaps, and various other release agents known to the art.

Adhesive tapes are especially suitable for use as member 32 of the present invention, and these are typified by No. 853 Mylar Adhesive Tape (Minnesota Mining and Manufacturing Co.) and Mystik Tape 7352 (Mystic Adhesive Products). However, if desired, a heat activated, rather than pressure activated adhesive tape may be used. For use in the present invention, transfer member 32 must be sufiiciently yieldable, flexible, soft or susceptible to impression, that the adhesive surface will in- Itimately contact photoconductive layer 11 except where contact is prevented by image 31. Thus, materials such as soft plastic sheets, adhesive-coated sheets of paper, metal, metal foils, as well as a wide variety of equivalent materials, are usable for transfer member 32.

Although specific embodiments and materials have been disclosed, these are not intended to limit the scope of the present invention. The claims append-ed hereto, therefore, should be interpreted broadly to encompass the specific disclosures herein and all reasonable equivalents.

What is claimed is:

1. An imaging process which comprises:

(a) forming an electrostatic charge pattern on the surface of an imaging member, said member comprising a support backing, a continuous non-blocking, release coating overlying said backing, and a photoconductive layer overlying said release coating, said photoconductive layer comprising from about 2 to about 20 parts photoconductive pigment per 1 part binder resin;

(b) developing said charge pattern with electroscopic marking particles, said particles being loosely held to the surface of said imaging member by electroconductive layer and said imaging member having retained on its surface in an imagewise manner complementary to that of the transfer member those photoconductive areas masked from the adhesive transfer member by said elecrtoscopic particles,

2. The process as disclosed in claim 1 wherein said release coating comprises a silicone release agent.

3. The process as disclosed in claim 1 wherein said imaging member further includes a background layer interpositioned between said rel-ease coating and said support backing.

4. The process as disclosed in claim 3 wherein said background layer comprises graphite.

5. An imaging process comprising:

(a) uniformly charging the surface of a photoconductive image support member, said member comprising a conductive support backing having fixed to the surface thereof a non-blocking, release layer overcoated with a photoconductive insulating layer, said photoconductive layer comprising from about 1 to about 20 parts photoconductive pigment per 1 part binder resin;

(b) selectively exposing said charged photoconductive member so as to form an electrostatic latent image on the surface thereof;

(c) developing said electrostatic latent image with electroscopic marking particles;

(d) contaoting the imaged surface of said member with an adhesive transfer member, said transfer member being such that the bond which exists between said adhesive member and said photoconductive layer is greater than the bond which exists between said photoconductive layer and said release layer; and

(e) separating said transfer member from said image support member so as to fracture said photoconductive layer in response to the adhesive forces of said transfer member, said transfer member having adhered to the surface thereof the electroscopic marking particles and the particle-free portions of said photoconductive layer and said image support member having retained on its surface in an image-wise manner complementary to that on the transfer member those photoconductive areas marked from the adhesive transfer member by said electroscopic particles.

'6. The process as disclosed in claim 5 further including the step of applying a protective coating to at least one of the image bearing surfaces of said transfer member and said photoconductive member.

7. The process as disclosed in claim 5 wherein said non-blocking layer comprises a silicone release film.

8. The process as disclosed in claim 5 wherein said image support member further includes a background layer interpositioned between said non-blocking, release layer and said conductive support backing.

9. The process as disclosed in claim 8 wherein said background layer comprises graphite.

10. The process as disclosed in claim 5 wherein said transfer member comprises a transparent flexible adhesive tape.

11. An image recording medium comprising a support backing, a continuous non-blocking, release coating overlying said backing, a background layer interpositioned between said release coating and said support backing, and a photoconductive layer overlying said release coaiting, said photoconductive layer comprising from about 2 to about 20 parts photoconductive pigment per 1 part binder resin.

12. The image recording medium of claim 11 wherein said background layer comprises graphite.

13. The image recording medium of claim 11 wherein said release coating comprises a silicone release film.

References Cited UNITED STATES PATENTS I. TRAVIS BROWN, Primary Examiner.

I. C. COOPER III, Assistant Examiner.

US. Cl. X.R. 

